regex visual studio - c++

Question

I was planning to use the following regex to capture path and name of a file:
std::regex capture_path_name_file("(.+)\\([^\\]+)\\.[^\\]+$");
but when running (i'm using visual studio) i get the regex error
error_brack: the expression contained mismatched [ and ]
Trying to pinpoint the cause i tried the following regex:
std::regex test("[^\\]")
and I got the same error.
I have tested my regex in regex101.com (with the slight difference that i had to use \. instead of \\.)
Thanks for any help.

Answer 1

The issue you have is because \\ is treated as 1 literal \ symbol in regular string literals. Biffen explained it well in his comment, [^\\] is treated as [^\], the ] is treated as a literal ] and not the closing character class delimiter (and there is no matching ] to close the character class further).
The right answer is: use _splitpath_s.
And if you want to further play with regex, you can fix it like this:
#include <iostream>
#include <regex>
using namespace std;
int main() {
std::regex rex1(R"((.+?)([^\\.]+\.[^\\.]+)$)");
std::smatch m;
std::string str = "c:\\Python27\\REGEX\\test_regex.py";
if (regex_search(str, m, rex1)) {
std::cout << "Path: " << m[1] << std::endl;
std::cout << "File name: " << m[2] << std::endl;
}
return 0;
}
Using raw string literals, you can avoid the majority of issues related to escaping. Use R"((.+?)([^\\.]+\.[^\\.]+)$)", it will match and capture into Group 1 the file folder path, and it will capture into Group 2 the file name with extension. Note that the extension must be present.